2. The blocked isocyanate containing emulsion composition of claim 1, said
emulsion composition having a core-shell structure in which said blocked
polyisocyanate component (A) forms a core part and said highly
crosslinkable polyurethane resin forms shell a part.

3. The blocked isocyanate containing emulsion composition of claim 1,
wherein the aqueous dispersed particle size distribution of the emulsion
is ranging from approximately 50 to 150 nm, and the weight ratio of
core/shell is ranging from approximately 50/50 to 70/30.

4. The blocked isocyanate containing emulsion composition of claim 1,
wherein said high molecular weight polyol (b2) has a carbonate skeleton
or a phthalate skeleton.

5. The blocked isocyanate containing emulsion composition of claim 1,
wherein said neutralizing agent is an amine compound, and said chain
extension agent is a polyamine compound.

8. An aqueous one-component coating composition that contains the blocked
isocyanate containing emulsion composition of claim 1 as a curing agent,
and a polyurethane based resin as a primary agent.

9. An aqueous one-component baking paint composition that contains the
blocked isocyanate containing emulsion composition of claim 1 as a curing
agent, and a polyurethane based resin as a primary agent.

Description:

FIELD OF THE INVENTION

[0001]The present invention relates to a blocked isocyanate containing
emulsion composition and production method thereof, and a baking paint
and adhesive compositions, and particularly relates to the emulsion
composition and the production method of the emulsion composition by
particular steps, in which the emulsion forms core-shell structures with
its particle size distribution made smaller and narrower while the
emulsion composition has an excellent storage stability even at the
temperature not less than 35 degrees Celsius and an excellent property
for coating agents.

[0002]Further present invention relates to an aqueous one-component baking
type paint and adhesive compositions that has an excellent coating
property and the like.

BACKGROUND ART

[0003]Polyurethane resin compositions have been widely used as coating and
adhesive agents, particularly as paints in a variety of industrial fields
such as automobiles, building materials, electric household appliances,
woodworks, etc., because of their excellent physical properties,
economical benefits, formability as well as applicability.

[0004]Recently, aqueous compositions that avoid the use of organic
solvents have particular importance in view of environmental preservation
and working safety, and have become more and more popular in use when
compared with the organic solvent based compositions because of their
economical advantage owing to non-use of the organic solvent. However, in
aqueous polyurethane resin coating agent, various material properties
thereof such as durability and solvent resistance are generally poor when
compared with those of organic solvent based coating agents. So efforts
for improvement have been continued so as to attain physical properties
nearly equivalent to those of organic solvent based coating agents.

[0005]As one of the improvement methods, an aqueous one-component
polyurethane emulsion which includes urethane pre-polymer being
introduced with carboxyl groups subjected to neutralization thereof to
provide aqueous dispersibility followed by emulsifying in water to
subject chain extension and another urethane pre-polymer immiscible with
water was disclosed (refer to Patent Literature 1). However, the entire
coating properties of the disclosed coating agents were still
insufficient.

[0006]As another advantageous method for improvements, an aqueous
one-component type polyurethane resin coating agent which utilizes so
called blocked isocyanate compounds (refer to, e.g. see Patent Literature
2) has been well known. Such kind of coating agents is so-called an
one-component baking type coating agent in which isocyanate groups are
blocked so as to inhibit progression of the cross-linking and curing at
room temperature and the coating layer thereof may be cured upon heating
due to the dissociation of blocking groups from isocyanate groups. The
above mentioned coating agents provide with various performances such as
water resistance and solvent resistance, or durability and adherence and
the like being superior to those of the coating film prepared from the
room temperature drying type. In order to further improve storage
stability etc., an aqueous baking type blocked polyurethane coating
agent, which use an isocyanate compound having nonionic hydrophilic group
together with an ionic surfactant, has been well known (refer to Patent
Literature 3). However, these aqueous blocked isocyanate containing
polyurethane coating agents of baking type are still insufficient in some
properties such as durability and solvent resistance as well as impact
resistance and gloss property when compared with those of organic solvent
based one, and water dispersability and storage stability thereof are
still insufficient.

[0007]Aqueous one-component coating polyurethane emulsions being prepared
by: mixing carboxyl group containing isocyanate-terminated urethane
prepolymer and non-anionic (nonionic) polyisocyanate; blocking the
isocyanate groups in a mixture by a blocking agent; neutralizing carboxyl
groups thereof; emulsifying in water; and then subjecting to chain
extension reaction by diamine was disclosed (Patent Literatures 4 and 5).
These polyurethane emulsions exhibited improved storage stability, water
resistance, solvent resistance, etc. of the film thereof. However, since
the blocked isocyanates were beforehand added in the aqueous dispersed
resin, amounts of the isocyanate groups being effective during thermal
dissociation of the blocking group were restricted, it was still
difficult to say that the properties for the coating or the adhesive
agent were sufficiently obtained.

[0013]Among the aqueous one-component type polyurethane resin coating
agents utilizing the blocked isocyanate compounds, the prior art aqueous
one component coating polyurethane emulsion, which was prepared by mixing
the non-anionic (nonionic) polyisocyanate with the carboxyl group
containing isocyanate-terminated urethane prepolymer; blocking the
isocyanate groups in the mixture with the blocking agent; neutralizing
the carboxyl groups in the mixture; emulsifying in water; and then
subjecting to chain extension reaction by the diamine, is the prior
invention filed by the same assignee. Since the aforementioned aqueous
one-component type coating polyurethane emulsion included beforehand the
blocked isocyanates and then the amounts of the isocyanate groups being
effective during thermal dissociation of the blocking group was
restricted. Also the storage stability at the temperature not less than
35 degrees Celsius was not sufficient yet. Hence, an object of the
present invention is to improve the previous aqueous one-component
coating polyurethane emulsion in order to improve aqueous dispersibility
and the storage stability of the emulsion as well as various coating
performances of the coating appearing around the dissociation temperature
of the blocking groups.

Means for Solving Problem

[0014]The inventors have aimed to overcome the above problems of the prior
inventions and have improved the previous aqueous one-component coating
polyurethane emulsion in order to improve the aqueous dispersibility and
the storage stability of the emulsion as well as various coating
performances of the coating appearing around the dissociation temperature
of the blocking groups by practical experimental examinations through try
and error in various viewpoints such as an embodiment for containing the
block isocyanate in the aqueous dispersion resin, an embodiment for
providing aqueous dispersibility functions, selections and combinations
of various reactive materials, reaction conditions for urethane-formation
reaction, etc. as well as conditions for emulsification to water and for
the chain extension etc.

[0015]In the course of the above-described examination, in order to
further improve the aqueous dispersibility and the storage stability of
the emulsion as well as various coating performances of the coating, the
inventors have found an completed the present invention characterized
mainly by forming blocked isocyanate through blocking of nonionic polar
group containing isocyanate, synthesizing in situ carboxyl group
containing isocyanate-terminated urethane prepolymer, and then subjecting
to emulsification and chain extension reaction after neutralization to
obtain emulsion particles with fine core-shell structures based on the
understanding that the embodiments for introducing the block isocyanate
into the aqueous dispersion resin though the blocking of the nonionic
polar groups containing polyisocyanate has the closest relevancy.

[0016]That is to say, the primary invention according to the present
inventions relates to an emulsion composition prepared by: synthesizing
carboxyl group containing isocyanate-terminated urethane prepolymer in
the reaction mixture where nonionic polar group containing blocked
polyisocyanate is generated to make use of the nonionic polar group
containing blocked polyisocyanate together with the carboxyl group
containing isocyanate-terminated urethane prepolymer, thereby forming a
core component (core part) from the nonionic polar group containing
blocked polyisocyanate and a shell (shell part) from the polyurethane
resin that is produced by neutralization and chain extension of the
carboxyl groups containing isocyanate-terminated urethane prepolymer, as
exemplarily shown in FIG. 1. (a).

[0017]More particularly, the primary invention according to the group of
the present inventions, relates to a blocked isocyanate containing
emulsion composition prepared by; reacting organic polyisocyanate (a1)
with nonionic polar group containing high molecular weight polyol (a2)
thereafter blocking isocyanate groups with a blocking agent (C) to form a
blocked polyisocyanate component (A); subsequently reacting, in the above
reaction mixture, organic polyisocyanate (b1), high molecular weight
polyol (b2), and anionic low molecular weight glycol containing a
carboxyl group (b3) to form carboxyl group containing
isocyanate-terminated urethane prepolymer (B); neutralizing carboxyl
groups in aforementioned reaction mixture by a neutralizing agent (D);
then emulsifying resulted reaction mixture in water; and further then
subjecting resulted emulsion to chain extension reaction by a chain
extension agent to prepare a highly crosslinkable polyurethane resin.

[0018]And, the blocked isocyanate containing emulsion composition with
particle size distribution of the aqueous emulsion from 50 to 150 nm and
with an weight ratio of core/shell from 50/50 to 70/30 reduces the
particle size distribution of the emulsion so that the aqueous
dispersibility and the storage stability thereof at the temperature not
less than 35 degrees Celsius may sufficiently improved and the coating
performances such as strength and uniformity appearing around the
dissociation temperature of the blocking groups may be enhanced.

[0019]As an optional feature or preferable embodiment according to the
group of the present inventions, the high-molecular weight polyol (b2)
may have a carbonate skeleton or a phthalate-skeleton, the neutralizing
agent may be an amine compound, and the chain extension agent may be a
polyamine compound, and the emulsion composition may be an aqueous baking
one-component type emulsion. Furthermore, a production method of the
blocked isocyanate containing emulsion composition according to the
present inventions has a primary aspect which includes the steps of:
forming a blocked polyisocyanate component (A); subsequently reacting, in
the above reaction mixture, organic polyisocyanate (b1), high molecular
weight polyol (b2), and anionic low molecular weight glycol containing a
carboxyl group (b3) to form carboxyl group containing
isocyanate-terminated urethane prepolymer (B), as described in paragraph
0009; The main usage of the blocked isocyanate containing emulsion
composition according to the present inventions, may be an aqueous
one-component coating composition that contains the blocked isocyanate
containing emulsion composition as a curing agent, and a polyurethane
based resin as a primary agent.

[0020]Here, providing the comparison between the present inventions and
the prior arts, it is clearly distinguished by referencing each of Patent
Literatures herein described in the paragraphs from 0003 to 0005 as the
background arts as well as other Patent Literatures that the present
inventions get ahead of the previous improvement methods for the blocked
isocyanate containing emulsion composition; when considering the prior
invention of the Patent Literature 4 and 5, the present inventions make
the emulsions particle size distribution narrower, the aqueous
dispersibility as well as the storage stability of the emulsion at the
temperature not less than 35 degrees Celsius are improved sufficiently,
and coating performance of various kind such as coating strength and
coating uniformity is improved. Furthermore, any of the prior references
fails to teach or suggest the primary aspect of the present inventions,
which includes the steps of: generating blocked isocyanate through
blocking of the nonionic polar group containing isocyanate; synthesizing
the carboxyl group containing isocyanate-terminated urethane prepolymer
in the above reaction mixture; and subjecting to emulsification and chain
extension reaction after neutralization as well as the principal feature
of the present inventions of providing the emulsion particles with fine
core-shell structures.

[0021]Hereinbefore, since the present inventions have been summarized by
means for solving the present problems in accordance with the
circumstance to invent the present inventions as well as the primary
configurations and features of the present invention: Here, overlooking
throughout the present invention to clarify the entire of the present
invention, the present inventions are composed of following group of
invention units, in which the inventions [1] and [2] represent the
primary inventions, and the inventions provided subsequently represent
practical examples or practical embodiments for the primary inventions
(the entire group of the inventions is herein referred to as "the present
inventions").

[0024][3] The blocked isocyanate containing emulsion composition of [1] or
[2], wherein the aqueous dispersed particle size distribution of the
emulsion is ranging from approximately 50 to 150 nm, and the weight ratio
of core/shell is ranging from approximately 50/50 to 70/30.

[0025][4] The blocked isocyanate containing emulsion composition of any
one of [1] to [3], wherein aforementioned high molecular weight polyol
(b2) has a carbonate skeleton or a phthalate skeleton.

[0026][5] The blocked isocyanate containing emulsion composition of any
one of [1] to [4], wherein aforementioned neutralizing agent is an amine
compound, and aforementioned chain extension agent is a polyamine
compound.

[0027][6] The blocked isocyanate containing emulsion composition of any
one of [1] to [5], wherein aforementioned emulsion composition is an
aqueous baking one-component type emulsion.

[0028][7] The production method of the blocked isocyanate containing
emulsion composition of any one of [1] to [6], aforementioned method
comprising the steps of: reacting organic polyisocyanate (a1) with
nonionic polar group containing high molecular weight polyol (a2)
thereafter blocking isocyanate groups with a blocking agent (C) to form a
blocked polyisocyanate component (A); subsequently reacting, in the above
reaction mixture, organic polyisocyanate (b1), high molecular weight
polyol (b2), and anionic low molecular weight glycol containing a
carboxyl group (b3) to form carboxyl group containing
isocyanate-terminated urethane prepolymer (B); neutralizing carboxyl
groups in aforementioned reaction mixture by a neutralizing agent (D);
then emulsifying resulted reaction mixture in water; and further then
subjecting resulted emulsion to chain extension reaction by polyamine to
prepare a highly crosslinkable polyurethane resin.

[0029][8] The aqueous one-component coating composition that contains the
blocked isocyanate containing emulsion composition of any one of [1] to
[6] as a curing agent, and a polyurethane based resin as a primary agent.

[0030][9] The aqueous one-component baking paint composition that contains
the blocked isocyanate containing emulsion composition of any one of [1]
to [6] as a curing agent, and a polyurethane based resin as a primary
agent.

[0031][10] The aqueous one-component baking adhesive composition that
contains the blocked isocyanate containing emulsion composition of any
one of [1] to [6] as a curing agent, and a polyurethane based resin as a
primary agent.

TECHNICAL ADVANTAGE OF THE INVENTION

[0032]According the present inventions, in the blocked isocyanate
containing emulsion composition, the emulsion particles are provided with
fine core-shell structures to make the emulsion particle size
distribution narrower, and then (i) the homogeneous emulsion without
impurity is obtained, (ii) the aqueous dispersibility and the storage
stability of the emulsion at the temperature not less than 35 degrees
Celsius are improved sufficiently (iii) various coating performances
appearing around the dissociation temperature of the blocking groups,
such as coating strength, coating uniformity and an outward appearance
thereof are improved so that the blocked isocyanate containing emulsion
composition may be quite useful as an organic solvent-free aqueous paint
or adhesion agent.

[0033]Furthermore, the aqueous emulsion composition according to the
present inventions (iv) is capable of forming a uniform film without
influence from environmental temperature and (v) provides with excellent
environmental preservation property, excellent working safety as well as
excellent handling property because of the aqueous nature thereof. Also,
the aqueous emulsion composition of the present inventions (vi) has high
productivity due to the simple production process thereof, and (vii)
exhibits excellent miscibility with primary agents of coating agents such
as polyurethane resins and modified polyolefin resins.

BEST MODE FOR CARRYING OUT THE INVENTION

[0034]The present inventions have been set forth along with the primary
configurations of the present invention depending on means for solving
the problems. Hereinafter, further detailed embodiment according to the
present invention of the above group of the inventions will be detailed.

[0036]The blocked isocyanate containing emulsion composition as the
primary invention of the invention group is the improvement about the
aqueous one component type polyurethane coating agent that uses the
blocked isocyanate compound and is featured as an aqueous emulsion in
highly crosslinkable self-dispersed type which includes
thermal-dissociable type blocked isocyanates.

[0037]In the aforementioned aqueous one-component type coating
polyurethane emulsion described in the paragraph 0006 as prior invention,
which is prepared by mixing the non-anionic (nonionic) polyisocyanate
with the carboxyl group containing isocyanate-terminated urethane
prepolymer; blocking the isocyanate groups of the mixture by the blocking
agent; neutralizing the carboxyl groups in the mixture; emulsifying the
mixture in water; and subjecting the obtained mixture to chain extension
reactions by the diamine, since the blocked isocyanates were introduced
into the aqueous-dispersed resin beforehand, the amounts of the
isocyanate groups being effective during the thermal dissociation was
restricted such that the aqueous dispersability and the storage stability
of the emulsion at the temperature not less than 35 degrees Celsius were
not still sufficient. In turn, the present inventions has been developed
the above previous aqueous one-component type coating polyurethane
emulsion further to improve the aqueous dispersability and the emulsion's
storage stability as well as to enhance various coating performances
appearing around the dissociation temperature of the blocking groups.

[0038]In the prior art, when the thermally dissociative blocked isocyanate
is prepared to paints or adhesive, almost of the main ingredients has
high viscosity such that the aqueous dispersibility and the handling
performance thereof are poor. In addition, when the ratio of the blocked
isocyanate is increased for performance improvement, the emulsion becomes
separated at the temperature not less than 35 degrees Celsius, because
the nonionic hydrophilic groups become a major ingredient. Furthermore,
film formability and outward appearance are likely to degrade due to
repellent of coating and phase separation. Furthermore, the composition
in which blocked isocyanate groups are introduced into the aqueous
dispersive type resin beforehand has the aspects in which the amount of
isocyanate groups being effective during thermal dissociation is
restricted and the aqueous dispersability and a storage stability of the
emulsion at the temperature not less than 35 degrees Celsius are
insufficient such that the coating performance could not be insufficient
and design flexibility as compositions for coatings or adhesives could be
narrower. Then, the present invention may also overcome the above
problems of the conventional art.

[0039]Therefore, the present inventions primarily based on: synthesizing
carboxyl group containing isocyanate-terminated urethane prepolymer in
situ in the reaction mixture where nonionic polar group containing
blocked polyisocyanate is generated, and after the neutralization thereof
emulsifying and extending the chain thereof in order to use the nonionic
polar group containing blocked polyisocyanate together with the carboxyl
group containing isocyanate-terminated urethane prepolymer as the main
feature.

[0041]As described in the paragraphs 0007 to 0008, the blocked isocyanate
containing emulsion composition of the present inventions is primarily
characterized in that the emulsion includes fine core-shell structures
(that is to say, almost nano-capsules) such that the nonionic polar group
containing blocked polyisocyanate forms the core components (core part)
while the strong flexible highly crosslinkable anionic polyurethane resin
that is obtained by neutralization and chain extension of the carboxyl
groups containing isocyanate-terminated urethane pre-polymer forms the
shell components (shell part) to provide the stably dispersed emulsion
composition as shown in FIG. 1. (a).

[0042]The blocked isocyanate containing emulsion composition, in which the
aqueous dispersed particle size distribution of the emulsion ranges from
50 to 150 nm and in which the weight ratio of core/shell ranges from
50/50 to 70/30, has the narrow emulsion particle size distribution such
that the aqueous dispersibility as well as the storage stability thereof
at temperature not less than 35 degrees Celsius are sufficiently improved
and the prevention of phase separation over long term is attained.
Furthermore, the coating performances appearing around the dissociation
temperature of the blocking groups, such as coating strength, coating
uniformity, outward appearance, etc. are improved and an uniform film may
be prepared without influence from environmental temperature while having
excellent immiscibility with the primary coating agent such as
polyurethane resins and modified polyolefin resins.

[0043]As for the comparison, as exemplarily illustrated in FIG. 1 (b), the
situation corresponding to the prior invention set forth in the paragraph
0006 herein is shown, where the nonionic polar group containing blocked
polyisocyanate dispersion forms core components, and the polyurethane
resins produced by neutralization and chain extension of the carboxyl
groups containing isocyanate-terminated urethane prepolymer are adhered
partially around the core component.

(3) The Properties of the Core-Shell Structures

[0044]According to the granularity (particle size) distribution
measurement, the emulsion composition having the core-shell structure of
the present invention was found to form an impurity-free homogeneous
emulsion and to consist an additional feature of the present inventions.
This novel feature has been explained as the advantage (i) in the
paragraph 0014.

[0045]More particularly, FIG. 2 shows the results of the granularity
distribution measurement of the emulsion composition according to present
invention, as the graph of granularity (micro-meter) versus frequency
(percentage); MICROTRAC HRA/VSR MODEL No. 9 320X100 (manufactured by
Leeds and Northrup Corp.) as a measurement instrument and pure water as a
solvent were used.

[0046]As the comparative example, FIG. 3 shows the results of the
measurements of granularity distribution of the admixed emulsion of the
nonionic polar group containing blocked polyisocyanate dispersion
(corresponding to the core component) and the polyurethane resin
(corresponding to the shell part) produced by neutralization and chain
extension from the carboxyl group containing isocyanate-terminated
urethane prepolymer. Similarly, FIGS. 4 and 5 show, as comparative
examples, the results of the measurements of the granularity
distributions of solo core and solo shell parts, respectively.

[0047]As clearly understood by comparison of each of figures, the emulsion
of the present invention shown in FIG. 2 shows the homogeneous particle
size distribution, and there is no particle size distribution indicating
the presence of impurity. In the comparative examples shown in FIGS. 3-5,
the distribution of some impurity particle other than the emulsion
particles were acknowledged at the larger particle size region.

[0049]The organic polyisocyanates (a1) and (b1) used in the process for
preparing the blocked polyisocyanate component (A) and the carboxyl group
containing isocyanate-terminated urethane prepolymer (B) may preferably
include organic diisocyanates. Such organic diisocyanates may include,
but not limited thereto, any conventional ingredients for polyurethane
resin. In order to avoid film yellowing due to UV light, aliphatic or
cycloaliphatic diisocyanates may be more preferable rather than aromatic
diisocyanates.

[0050]To avoid complicated descriptions and also to provide the essential
descriptions for simplifying the description, the following exemplary
explanation for each of compounds may be simplified, however, such
simplification does provide no influence on the essential parts of the
present invention.

[0051]Particularly, the aliphatic diisocyanate may include, such as, for
example, tetramethylene diisocyanate, hexamethylene diisocyanate, lysine
diisocyanate, 2-methylpentane-1,5-diisocyanate,
3-methylpentane-1,5-diisocyanate,
2,2,4-trimethylhexamethylene-1,6-diisocyanate, and
2,4,4-trimethylhexamethylene-1,6-diisocyanate. Aromatic diisocyanate may
include, such as, for example, isophorone diisocyanate, cyclohexyl
diisocyanate, hydrogenated xylylene diisocyanate, hydrogenated
diphenylmethane diisocyanate, hydrogenated trimethyl xylylene
diisocyanate. These diisocyanates may be used solely or used in any
admixture of more than two species.

[0053]In consideration of the durability and the adherence of coatings
formed from the aqueous polyurethane emulsion obtained by the present
inventions, the base polyisocyanate for the nonionic polar group
containing polyisocyanate may preferably include isocyanurate
modifications and complex-modifications prepared from aliphatic
diisocyanates and/or cycloaliphatic diisocyanates.

[0055]The high molecular weight polyol used in the process for forming the
blocked polyisocyanate may include, such as, for example, polyols which
contain nonionic polar group to give the blocked polyisocyanate a
hydrophilic nature. For examples, polyalkylene polyols that contain usual
polar alkoxy groups as the nonionic polar groups may be available.

[0056]Of course, usual nonionic polar group containing polyester polyols
and polycarbonate-polyols may be also available.

[0057]The part for the high molecular weight polyol may preferably have
their number-averaged molecular weight from 500 to 10,000, and more
preferably from about 500 to 5,000.

(iii) Blocking Agent (C)

[0058]The blocking agent (C) used in the present invention is not limited
particularly, and may be appropriately selected at least one compound
from known compounds. The blocking agents may include, such as, for
example, phenol group compounds, alcohol group compounds, active
methylene group compounds, mercaptan group compounds, acid amid group
compounds, lactam group compounds, acid imide group compounds, imidazole
group compounds, urea group compounds, oxime group compounds, amine group
compounds, etc.

[0059]More particularly, the phenol group compounds may include, such as,
for example, phenol and cresol, ethylphenol; the alcohol group compounds
may include such as propylene glycol monomethyl ether, ethylene glycol,
benzylalcohol, methanol and ethanol; the active methylene group compounds
may include such as dimethyl malonate and acetylacetone; the mercaptan
group compounds may include such as butyl mercaptan and dodecyl
mercaptan; the acid amid group compounds may include such as acetonitride
and acetic acid amide; the lactam group compounds may include such as
epsilon-caprolactam and delta-valerolactam; the acid imide group
compounds may include such as succinic acid imide and maleic acid imide;
the oxime group compounds may include such as acetaldoxime, acetone oxime
and methyl ethyl ketoxime; the amine group compound may include such as
diphenylaniline, aniline and ethyleneimine. In view of availability and
working performance, the methyl ethylketoxime, epsilon-caprolactam and
2-ethylhexanol may be preferably used in the present invention among the
aforementioned blocking agents.

(iv) High Molecular Weight Polyol (b2)

[0060]The high molecular weight polyol (b2) used in the process for
preparing the carboxyl group containing isocyanate-terminated urethane
prepolymer may include, such as, for example, polyester polyol,
polyesteramide polyol, polyether polyol, polyether-ester polyol,
polycarbonate polyol, polyolefin polyol that have normally a number
average molecular weight from 500 to 10,000, more particularly, from 500
to 5,000, and any admixture thereof. Here, when considering the water
durability of the shell part, the high molecular weight polyols having
carbonate skeletons or phthalate skeletons may be preferable.

[0061]The polyester polyols and the polyesteramide polyols may include,
for example, those obtained through the reaction between any of the
polycarboxylic acid derivatives such as polycarboxylic acids, acid
esters, acid anhydrides or acid halides and any of low molecular weight
polyol, low molecular weight polyamine or low molecular weight amino
alcohol etc. with the number average molecular weight thereof being less
than 500.

[0062]The carboxyl group containing anionic low molecular weight glycol
(b3) used in the process for preparing the carboxyl group containing
isocyanate-terminated urethane prepolymer, may be incorporated into the
backbone of the prepolymer through the reaction of the active hydrogens
of the hydroxyl groups at both terminals with the isocyanate groups so
that the aqueous dispersibility of the prepolymer may be enhanced due to
hydrophilic nature of the carboxyl group. The carboxyl group may provide
further enhancement of the aqueous dispersibility through additional
neutralization.

[0063]The carboxyl group containing low molecular weight glycol may
include, such as, for example, dimethylol propionic acid and dimethylol
butanic acid, which have two terminal hydroxyl groups, other reaction
products prepared from polyamines with acid anhydrides, and lacton
adducts obtained by using dimethylol propionic acid, dimethylol butanic
acid or the like as an initiated agent.

(vi) Neutralizing Agent

[0064]The neutralizing agent of the present invention may be optionally
used and the neutralizing agent may include any conventional neutralizing
agents. The neutralizing agent preferably may include, for example,
organic amines such as ethylamine, trimethylamine, triethylamine,
triisopropylamine, triethanolamine, triisopropanolamine, morpholine and
N-methylmorpholine; and inorganic alkalis such as sodium hydroxide,
potassium hydroxide and ammonia. In order to enhance climate resistance
and water resistance of dried film, the neutralizing agent may preferably
include volatile one that easily dissociates by heating, and amino
alcohols reactive to polyisocyanate curing agents.

(vii) Chain Extension Agent

[0065]The chain extension agent may preferably include, but not limited
thereto, diamime compounds and polyamine compounds in term of various
physical properties such as water resistance, solvent resistance and
pollution resistance because they lead to crosslinking highly and easily
when compared with diol compounds as the chain extension agent. The amine
compounds may include, for example, diamines such as ethylene diamine
(EDA) and isophorone diamine (IPDA), and polyamines such as
diethylenetriamine (DETA), triethylenetriamine, tetraethylenepentamine
and pentaethylenehexamine, which are represented by the general formula:
H2N--(C2H4NH)n--C2H4NH2 (n=1 to 8).

(viii) Curing Catalysts and Curing Agents

[0066]A resin-formation catalyst (urethane-formation catalyst) as a curing
catalyst (polymerization catalyst) for urethane reaction may be
optionally used, if necessary. Conventional curing catalysts may be
available and may include, for example, metal catalysts such as dibutyl
tin dilaurate and zinc naphthenate, and amine catalysts such as
triethylenediamine and N-methylmorpholine such that the reaction rate may
increase and the reaction temperature may be lowered.

[0067]The curing agents for curing the polyurethane resin, may include
trimers and adducts with more than three NCO groups in single molecule,
that are derived from a hexamethylene diisocyanate (HDI) or a isophorone
diisocyanate (IPDI).

[0069]The production method of the blocked isocyanate containing emulsion
composition according to the present inventions primary comprises the
steps of: reacting organic polyisocyanate (a1) with nonionic polar group
containing high molecular weight polyol (a2) thereafter blocking
isocyanate groups with a blocking agent (C) to form a blocked
polyisocyanate component (A); subsequently reacting, in situ in the
reaction mixture, organic polyisocyanate (b1), high molecular weight
polyol (b2), and anionic low molecular weight glycol containing a
carboxyl group (b3) to form carboxyl group containing
isocyanate-terminated urethane prepolymer (B); neutralizing carboxyl
groups in the reaction mixture by a neutralizing agent (D); then
emulsifying resulted reaction mixture in water; and further then
subjecting resulted emulsion to chain extension reaction by a polyamine.

[0070]Particularly, in accordance with the primary aspect in which
nonionic polar group containing isocyanate is blocked to form the blocked
polyisocyanate and; and in situ in that reaction mixture, the carboxyl
group containing isocyanate-terminated urethane prepolymer is
synthesized; the emulsion particles form fine core-shell structures such
that the aforementioned advantages (i) to (vii) of the present invention
described in the paragraph 0014 are provided.

[0071]The blocking reaction may be carried at the temperature from 20 to
100 degrees Celsius, more preferably, from 30 to 90 degrees Celsius as
the conventional condition for block reaction. At this time, any
well-known urethane-formation catalysts may be used. The blocking ratio
may be preferably not less than 20 mol-percent, more preferably, may
range from 30 to 50 mol-percent.

[0072]When the blocking ratio was too low, the strength and durability of
the film tends to become insufficient.

[0073]Any known urethane-formation catalysts may be allowed to use during
the production process of the carboxyl group containing
isocyanate-terminated urethane prepolymer. The reaction temperature may
preferably range from 0 to 100 degrees Celsius, more preferably, from 20
to 90 degrees Celsius. At this time, diluting into any solid contents by
any organic solvent that is substantially inactive to isocyanate group
may be preferable in terms of mixing efficiency. The organic solvents may
include, for example, aromatic solvents such as toluene and xylene;
aliphatic hydrocarbon solvents such as hexane; cycloaliphatic solvents
such as cyclohexane and isophorone; ketone solvents such as acetone and
methyl ethyl ketone; ester solvents such as ethyl acetate and butyl
acetate; glycol ether ester solvents such as ethylene glycol monoethyl
ether acetate and propylene glycol mono-methyl ether acetate; glycol
ether solvents such as ethylene glycol dimethyl ether diethylene glycol
dibutyl ether and propylene glycol dibutyl ether.

[0074]Neutralization may be carried out by using various neutralizing
agents described in paragraph 0031, under usual neutralization reaction
condition that ranges from 20 to 50 degrees Celsius.

[0075]3. Aqueous Polyurethane Resin Emulsion Coating Composition

(1) Primary Agent and Curing Agent

[0076]The aqueous polyurethane resin coating composition according to the
present invention corresponds to applied embodiments originated from the
primary invention of the present inventions, and may be used for coating
agents (paints) and adhesive agents. The aforementioned coating
composition may be primary composed from a primary agent and a curing
agent, the block isocyanate containing emulsion composition may be used
as the curing agent, and any conventional polyurethane resins or modified
polyolefin resins may be used as the primary agent, appropriately.

(2) Embodiments of Practical Use

[0077]After applied on any one of various conventional substrates such as
metals, plastics, woody materials and inorganic materials as a coating
agent, the aforementioned coating composition could be cured and baked
thereon by heating of the coated film, in which the blocking groups
dissociates so that isocyanate groups undergo cross-linking reaction with
active hydrogens highly.

(3) Additives

[0078]In order to enhance various physical properties even more, and to
give some additional physical properties other than the aforementioned
physical properties, some of the optional additives may be available. The
optional additives may include anti-flammable agents, plasticizer agents,
antioxidant agents, UV ray absorbing agents, dyes, pigments, fillers,
internal de-molding agents, reinforcing agents, matting agents,
electronic conductivity importing agents, charge control agents,
antistatic agents, lubricants and other processability-enhancing
additives.

EXAMPLES

[0079]Hereinafter, the present inventions will be practically described in
detail to clarify the feature of the present inventions by examples while
comparing with comparative examples, and the rationality and the
significance of the each features of the present invention as well as the
excellence thereof compared to the conventional arts will be
demonstrated.

[0081]The organic polyisocyanate (a1) was subjected to the reaction with
the nonionic polar group containing high-molecular weight polyol (a2);
thereafter the isocyanate groups were blocked by the blocking agent (C)
to form the blocked polyisocyanate component (A); subsequently, in situ
in the above reaction mixture, the organic polyisocyanate (b1), the
high-molecular weight polyol (b2) and the carboxyl group containing
anionic low-molecular weight glycol (b3) were reacted to prepare the
carboxyl group containing isocyanate-terminated urethane prepolymer (B);
then the carboxyl groups in the reaction mixture were neutralized by the
neutralization agent (D); after that, the resulted reaction mixture was
emulsified in water; and further the resulted emulsion was subjected to a
chain extension reaction by polyamine.

[0084]In a four-necked 1-L separable flask equipped with a stirrer having
anchor type fans, a thermometer and a condenser, 158 g of the isocyanate
B, 26.0 g of the polyol B, 27.8 g of the solvent B and 0.001 g of the
urethane-formation catalyst were charged and were heated at 85 degrees
Celsius for 2 to 3 hours with stirring to cause the urethane reaction.
Then, the reaction mixture was cooled while keeping its temperature
between 80 and 40 degrees Celsius. The blocking agent of 66.0 g was
charged in a dropping funnel and was dropped into the reaction mixture
over a period of 30 minutes to 1 hour. Then, the reaction mixture was
subject to the reaction at 70 to 80 degrees Celsius for additional 2
hours to complete the reaction. After that, the NCO content therein was
measured to confirm that the measured value was not more than 0.1
weight-percent.

[0085]Thereafter, to the resulted blocked isocyanate intermediate, 115 g
of the polyol A, 1.2 g of the low molecular weight glycol, 7.6 g of the
anionic hydrophilic group component and 50 g of the solvent A were added
and dissolved with stirring at 80 to 90 degrees Celsius for 1 hour. After
being cooled to the 70 to 80 degrees Celsius, 40.3 g of the isocyanate A
was added and subjected to the reaction with stirring at 80 to 90 degrees
Celsius for 3 hours. After confirming that the hydroxyl groups and the
isocyanate groups were reacted equivalently, the product was cooled to 50
to 60 degrees Celsius followed by addition 8.2 g of the isocyanate B.
After stirring for approximately 30 minutes, 5.8 g of the neutralizing
agent was added, the stirring was continued for approximately 30 minutes
at 50 to 60 degrees Celsius.

[0086]Into the liquid mixture, 450 g of room temperature water was dropped
with stirring at 300 rpm over a period of 2 minutes. At 30 minutes after
the completion of the dispersion, 21 g of room temperature 15 percent
aqueous solution of organic amine prepared beforehand was dropped. High
speed stirring was kept for 1 hour to obtain milky white target material.
Then, the stirring speed was reduced to normal rate (about 100 rpm) and
the stirring was continued at 50 to 60 degrees Celsius for additional 2
hours.

[0087]By using FT-IR, the absence of peaks originated from the NCO residue
was confirmed. The resulted non-volatile residue of the target material
was 43 percent with a viscosity of 63 mPa s (at 25 degrees Celsius) and
an average dispersed particle size of 136 nm.

[0091]A steel plate (SPCC-SB supplied by Paltec Test Panels Co., ltd.) was
applied with 100 micro-meter in wet by using an applicator, and after
drying at room temperature for 5 minutes, and the coated film was further
dried in a temperature-gradient oven (gradient-oven manufactured by BYK
Gardner) at 100 to 200 degrees Celsius for 30 minutes.

[0092](Outward appearance observations) The outward appearances of the
coated films, each of which was obtained by drying/baking at each
temperature described in Table 2, were visually inspected, and evaluated
whether there was any tuck, whether mat or clear and whether there was
any roughness and the like.

[0093](Pencil hardness tests) Pencil hardness which gave scratches to the
dried and baked coating film obtained at each temperature of Table 2 was
examined and proved.

[0094](MEK rubbing tests) In each coated film that was obtained by
dried/baked at each temperature of Table 2, a cotton swab which were
soaked slightly with methyl ethyl ketone (MEL) was moved reciprocally on
the coated film, numbers of round trips just before the coated film was
worn off or peeled off were measured.

[0095](Water resistance tests) After each coated film which was obtained
by dried/baked at each temperature of Table 2, was immersed in boiling
water for 12 hours, the outward appearance thereof was inspected
visually, and the good outward appearance was marked by a circle mark and
bad outward appearance was evaluated by a cross mark, respectively.

[0096]Table 2 summarizes the results of the evaluation tests of the
coating agents.

The Considerations of the Results of the Examples and the Comparative
Examples

[0097]As shown in Table 1, providing the comparison between the each of
examples and each of comparative examples, it was indicated that the
blocked isocyanate containing emulsion compositions (the examples A and
B) of the present invention provided good liquid outward appearance and
hence had excellent aqueous dispersibility even after one week under 50
degrees Celsius. In contrast, the comparative example B, that contained
no polyurethane resin formed by subjecting the carboxyl group containing
isocyanate-terminated urethane prepolymer to neutralization and chain
extension, was found to cause two-phase separation; the comparative
example A, that was cold blend resin of a component of the comparative
example B and an urethane primary agent of the comparative example C, was
found to cause precipitation; both of which lacked aqueous
dispersibility.

[0098]As shown in Table 2, the blocked isocyanate containing emulsion
compositions of either examples A or B (as shown composition 1 and
composition 2, respectively) failed in exhibiting good coating
performances such as outward appearance, pencil hardness, MEK rubbing,
and water resistance, because they were not composed as the coating agent
(paint) yet. The compositions 3 and 4 corresponding to the aqueous
one-component type coating agent according to the present inventions,
which were composed from the blocked isocyanate containing emulsion
composition of the example B and the urethane primary agent of
comparative examples C and D, respectively, were found to provided good
coating film performances such as outward appearance, pencil hardness,
MEK rubbing and water resistance. The compositions 5 to 7, each of which
contained no blocked isocyanate containing emulsion composition of the
present invention, were found to provide significantly poor coating film
performances such as outward appearance, pencil hardness, MEK rubbing and
water resistance when compared with that of the present inventions.

[0099]Hereinabove, from the comparison and the consideration of resulted
data of each example and each comparative example, together with the
consideration of the novel properties of the core-shell structures
according to the present inventions, it may be concluded that the
rationality and the significance of the features according to the present
invention have been demonstrated and the present inventions have the
remarkable excellence compared to the conventional arts.

BRIEF DESCRIPTION OF THE DRAWINGS

[0100]FIG. 1 shows the schematic cross-sectional views of (a) the
core-shell structure according to the present invention, and (b) the
emulsion structure according to the comparative example A.

[0101]FIG. 2 is the graph showing the result of the granularity
distribution of the emulsion composition according to present invention.

[0102]FIG. 3 is the graph showing the result of the granularity
distribution of the admixed emulsion of the core component and the shell
component.

[0103]FIG. 4 is the graph showing the result of the granularity
distribution of the emulsion of only the core component.

[0104]FIG. 5 is the graph showing the result of the granularity
distribution of the emulsion of only the shell component.